Blue-green algae has reappeared at Camlough Lake near Newry and Craigavon Lakes in Northern Ireland during a spell of warm summer weather, forcing closures and warnings that are hitting local businesses and communities. The toxic bacteria, which can cause skin irritation and sickness in people and animals, has become a recurring summer problem, and its timing this year is especially damaging as it coincides with peak visitor season. Business owner Karl Toner, who runs a coffee cart, glamping site and paddleboard hire business at Camlough Lake, said the closure has emptied a normally busy lake, comparing it to "having an amusement park and not opening it".

According to the UK Centre for Ecology and Hydrology, there are currently 247 algae blooms across Lough Neagh and Northern Ireland's water systems, with 80 confirmed in June and July alone. Warning signs went up at Camlough Lake on 13 July after Daera notified Newry, Mourne and Down District Council, which is monitoring the lake and arranging toxin testing until safety criteria are met. Craigavon Lakes suspended watersports and open-water swimming on 21 July for the same reason. Open-water swimmer Joanne Callan said the closures affect a community of more than 100 regular swimmers, while Daera said there are "no quick fixes" but restoring water quality is possible through science-led, if difficult, decisions.